The main text is my interpretation2 of what Blackburn says, with my specific comments and objections appearing as footnotes.

Exposition / Comments by Section

The Unity Reaction

Blackburn starts off with – effectively – a potted defense of animalism3.

From the third-person perspective, there are no obvious problems with personal identity that don’t arise when we consider the identity over time of other large mammals, which is what we are4.

While we have complex psychologies, these are just properties that change over time.

He does, however, say that these psychologies “are in certain respects universal5”.

So, if we are not troubled by stories of fission or fusion, or Sorites6 cases, when applied to chimpanzees, we should not be worried when these are applied to persons7.

So there are no obvious problems with third-person re-identification in normal circumstances. And in the case of unusual (imagined) circumstances we’d find our way round it as we would with the fission or fusion of animals, plants or ships – though it would matter more to us that we came to the right conclusion.

So, if a friend fissioned, we’d then become reconciled to having two friends – though Blackburn notes Lewis’s “arithmetic8”, where there were two friends all along. If this sort of thing was common – and could be foretold – we’d avoid making future predications implying uniqueness.

It’s only from the first-person perspective that problems may arise.

Even there it’s the future9 rather than the past that’s troubling – I can get my head around tales of my past fissioning10 or even fusion11. But if I think of future my own future fissioning – especially if the fission products enjoy or suffer radically different fates – I can only imagine one of three possible outcomes. I will be one, the other, or neither12. I will not be enjoying some middle-ground experience, but only one of the alternatives, or nothing at all.

Nor can Blackburn imagine the split-brain13 case described by Parfit14 in “My Physics Exam”, where one half of my brain solves a physics problem while the other half talks to a friend. The two activities are mutually exclusive.

This is what is intended by the Section’s title “The Unity Reaction”.

Blackburn is unsure how much weight should be attached to this Reaction. It may be a hang-over from beliefs in Cartesian Egos15 – though it is surely a motivator for – rather than a consequence of – such beliefs.

Blackburn has a swipe at Reincarnation, Telepathy and the like16 – which are not independent evidence for Pure Egos.

Cartesianism explains (wrongly) the Unity Reaction by positing a “definite something” that is unaffected by whatever is happening to the animal and its psychology, and which consequently ends up in one or other (or neither) of the fission products. Kant has (it seems17) shown the uselessness of such a hypothesis. Yet (says Blackburn) it’s only on such a “theory” that we have a problem of identity as such18. Otherwise, it’s just a question of integrating our thoughts about the self19.

Origins of the Unity Reaction aside, can we train ourselves out of it, as some suggest this might have metaphysical and even ethical benefits? Blackburn wants to dispute this, and will do so from the Kantian standpoint of the “active subject of thought and action”. Blackburn wants to explore Kant’s idea that the unity of the self is forced on us by this standpoint; and so-doing will loosen a central plank of "Parfit (Derek) - Reasons and Persons".

It seems that Parfit is proposing20 a “non-practical ‘constitutive’ metaphysics of the self”, but Blackburn thinks this cuts no ice contra a “practical stance such as egoism”.

Practical reasoning – and planning a future project – both require us to ask “how will it be for me”, and this activity “maintains an absolute, but formal, grip on the self”, which explains the Unity Reaction, whatever or not the empirical self is seen as dissolved, merged or split in a TE.

Blackburn points out that the ethical claim – that nice people might be happier if good things happened to others rather than to themselves (they might “have what matters” in such circumstances) – just changes the subject. If my project is for this good thing to happen to me, it fails if it happens to someone else.

So, even if Parfit’s metaphysics is correct, the ethical consequences are less than he imagines. The standpoint of practical reason is a constraint on the truth about persons.

He now wants to say something about the standard “Strawsonian” objection to Humean or Parfitian reductionism.

Parfit and the Kantian. Both equally hostile to Cartesian Egos, though only empirically for Parfit.

Parfit: persons exist, but we can give a complete account of reality without mentioning them. Probably not an error theorist. Analogy with Communities and the people that make them up.

The relation of whether an impersonal description is complete to deducibility. Statues and particles & their relations. Do persons follow from bodies and non-branching continuity and connectedness between psychological states?

Non-vicious circular ontological dependence of parts and wholes. Analogy of sounds and tunes. But have we any conception of a perception or psychological state in abstraction from its owner?

Second objection: contents of thoughts presupposing the Unity Relation and the existence of Parfit’s selves or irreducible Selves. Bernard Williams’s “Government House” line (vulgar illusion) not open to Parfit, whose ethical theory depends on us believing the truth about ourselves. Still, we need a Kantian undermining of the reductionist’s starting point.

The Self in Space

Focus on psychological atoms – are they constitutively dependent on Selves that cannot be replaced by a reductionist substitute?

Blackburn won’t adopt the third-person approach – which treats thoughts as dependent on Selves at dents and bruises on bodies. It doesn’t take the Unity Reaction seriously enough to engage with what troubles us.

Outline of the Kantian/Strawsonian account of perception of the world. The organisation requires an organiser with a self-conception. Reference to "Cassam (Quassim) - Kant and Reductionism". Programming and Camera objections.

I’m finding some of what Blackburn says difficult to construe. Consequently, my notes are somewhat plodding until I can see the light.

From Section 2 onwards, I’ve just added (maybe inaccurate) indicators of what each paragraph is about.

I was alerted to this paper by Lawrence M. Hinman, Ph.D. Professor Emeritus, University of San Diego, who was after a copy, but eventually obtained one from Simon Blackburn himself. For Hinman, see Link (Defunct) and Link (Defunct).

He was “sitting in on a seminar that Jeff Blustein (presumably Link) and Bill Ruddick (presumably Link (Defunct)) are giving on ethical issues in memory, and we were discussing Parfit on personal identity and memory. In any case, I expect Blackburn's article might help me to clarify some of my reservations about Parfit.”

He says that they could be duplicated. I’d thought that what this implies is that psychologies (or at least the contents of them) are software, or data, universals in any case, so can be realised on many hardware platforms. But, they are not us. We are the hardware on which the software runs.

But, his full text is “Complex psychologies … give us a psychological form that is in certain respects universal, so that it could be duplicated, and shared with others of our kind who have had the same experiences or have the same mental traits. ”

I don’t know what he means by the latter part of this sentence. I’d like it to say “who would then appear to have had the same experiences and would then have the same mental traits”.

Is this describing a thought-experiment, or saying something more prosaic (and less relevant) about the psychological similarities of people with similar experiences and mental traits, which lays the way for the Parfitian thought experiments?